[PATCH 0/2] fast-import: allow more operations on root directory

@@ -2951,6 +2951,9 @@ static void parse_ls(struct branch *b)
 	} else {
 		struct object_entry *e = parse_treeish_dataref(&p);
 		root = new_tree_entry();
+		hashclr(root->versions[0].sha1);
+		root->versions[0].mode = 0;
+		root->versions[1].mode = S_IFDIR;
 		hashcpy(root->versions[1].sha1, e->idx.sha1);
 		load_tree(root);
 		if (*p++ != ' ')

@@ -1552,6 +1552,31 @@ static int tree_content_set(
 	return 1;
 }
 
+static int tree_content_clear(
+	struct tree_entry *root,
+	struct tree_entry *backup_leaf)
+{
+	if (backup_leaf)
+		memcpy(backup_leaf, root, sizeof(*backup_leaf));
+	else if (root->tree)
+		release_tree_content_recursive(root->tree);
+	root->tree = NULL;
+	hashclr(root->versions[1].sha1);
+	return 1;
+}
+
+static int is_empty_tree(struct tree_entry *root)
+{
+	int n;
+	if (!root->tree)
+		load_tree(root);
+	for (n = 0; n < root->tree->entry_count; n++) {
+		if (root->tree->entries[n]->versions[1].mode)
+			return 0;
+	}
+	return 1;
+}
+
 static int tree_content_remove(
 	struct tree_entry *root,
 	const char *p,

@@ -1587,11 +1612,9 @@ static int tree_content_remove(
 			if (!e->tree)
 				load_tree(e);
 			if (tree_content_remove(e, slash1 + 1, backup_leaf)) {
-				for (n = 0; n < e->tree->entry_count; n++) {
-					if (e->tree->entries[n]->versions[1].mode) {
-						hashclr(root->versions[1].sha1);
-						return 1;
-					}
+				if (!is_empty_tree(e)) {
+					hashclr(root->versions[1].sha1);
+					return 1;
 				}
 				backup_leaf = NULL;
 				goto del_entry;

@@ -1613,6 +1636,19 @@ del_entry:
 	return 1;
 }
 
+static int tree_content_copy_root(
+	struct tree_entry *root,
+	struct tree_entry *leaf
+)
+{
+	memcpy(leaf, root, sizeof(*leaf));
+	if (root->tree && is_null_sha1(root->versions[1].sha1))
+		leaf->tree = dup_tree_content(root->tree);
+	else
+		leaf->tree = NULL;
+	return 1;
+}
+
 static int tree_content_get(
 	struct tree_entry *root,
 	const char *p,

@@ -2329,10 +2365,17 @@ static void file_change_cr(struct branch *b, int rename)
 	}
 
 	memset(&leaf, 0, sizeof(leaf));
-	if (rename)
-		tree_content_remove(&b->branch_tree, s, &leaf);
-	else
-		tree_content_get(&b->branch_tree, s, &leaf);
+	if (rename) {
+		if (!*s)
+			tree_content_clear(&b->branch_tree, &leaf);
+		else
+			tree_content_remove(&b->branch_tree, s, &leaf);
+	} else {
+		if (!*s)
+			tree_content_copy_root(&b->branch_tree, &leaf);
+		else
+			tree_content_get(&b->branch_tree, s, &leaf);
+	}
 	if (!leaf.versions[1].mode)
 		die("Path %s not in branch", s);
 	if (!*d) {	/* C "path/to/subdir" "" */

@@ -2342,6 +2385,14 @@ static void file_change_cr(struct branch *b, int rename)
 			leaf.tree);
 		return;
 	}
+	/*
+	 * Git does not track empty, non-toplevel directories.
+	 * At this point destination is non-toplevel, so if source is
+	 * toplevel and empty, leave it as is all empty.
+	 */
+	if (!*s && is_empty_tree(&leaf)) {
+		return;
+	}
 	tree_content_set(&b->branch_tree, d,
 		leaf.versions[1].sha1,
 		leaf.versions[1].mode,

@@ -2969,7 +3020,11 @@ static void parse_ls(struct branch *b)
 			die("Garbage after path in: %s", command_buf.buf);
 		p = uq.buf;
 	}
-	tree_content_get(root, p, &leaf);
+	if (!*p) {
+		if (!is_empty_tree(root))
+			tree_content_copy_root(root, &leaf);
+	} else
+		tree_content_get(root, p, &leaf);
 	/*
 	 * A directory in preparation would have a sha1 of zero
 	 * until it is saved.  Save, for simplicity.

@@ -978,6 +978,64 @@ test_expect_success PIPE 'N: empty directory reads as missing' '
 '
 
 test_expect_success \
+	'N: ls root directory' \
+	'cat >expect <<-\EOF &&
+	missing
+	040000
+	EOF
+	cat >input <<-EOF &&
+	commit refs/heads/ls-root
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	On empty tree: ls add file ls.
+	COMMIT
+	ls ""
+	M 644 inline file1
+	data 0
+	ls ""
+	EOF
+	git fast-import --quiet <input >tmp &&
+	cat tmp | cut -d " " -f 1 >actual &&
+	test_cmp expect actual'
+
+test_expect_success \
+	'N: move root directory' \
+	'echo "root/a/b" >expect &&
+	cat >input <<-EOF &&
+	commit refs/heads/move-root
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	Add stuff and move it.
+	COMMIT
+	M 644 inline a/b
+	data 0
+	R "" root
+	EOF
+	git fast-import <input &&
+	git ls-tree -r --name-only refs/heads/move-root >actual &&
+	test_cmp expect actual'
+
+test_expect_success \
+	'N: copy root directory' \
+	'cat <<-\EOF >expect &&
+	a/b
+	a/root/a/b
+	EOF
+	cat >input <<-EOF &&
+	commit refs/heads/copy-root
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	Add stuff and move it.
+	COMMIT
+	M 644 inline a/b
+	data 0
+	C "" a/root
+	EOF
+	git fast-import <input &&
+	git ls-tree -r --name-only refs/heads/copy-root >actual &&
+	test_cmp expect actual'
+
+test_expect_success \
 	'N: copy root directory by tree hash' \
 	'cat >expect <<-\EOF &&
 	:100755 000000 f1fb5da718392694d0076d677d6d0e364c79b0bc 0000000000000000000000000000000000000000 D	file3/newf

@@ -3019,7 +3019,7 @@ static void parse_ls(struct branch *b)
 			die("Garbage after path in: %s", command_buf.buf);
 		p = uq.buf;
 	}
-	if (*p) {
+	if (*p || root != &b->branch_tree) {
 		tree_content_get(root, p, &leaf);
 	} else {
 		leaf = *root;

@@ -1400,8 +1400,72 @@ test_expect_success \
 	 test_cmp expect.qux actual.qux &&
 	 test_cmp expect.qux actual.quux'
 
+test_expect_success 'N: root of unborn branch reads as present and empty' '
+	empty_tree=$(git mktree </dev/null) &&
+	echo "040000 tree $empty_tree	" >expect &&
+	git fast-import --cat-blob-fd=3 3>actual <<-EOF &&
+	commit refs/heads/N-empty
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	read empty root directory via ls
+	COMMIT
+
+	ls ""
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'N: empty root reads as present and empty' '
+	empty_tree=$(git mktree </dev/null) &&
+	echo "040000 tree $empty_tree	" >expect &&
+	echo empty >msg &&
+	cmit=$(git commit-tree "$empty_tree" -p refs/heads/branch^0 <msg) &&
+	git fast-import --cat-blob-fd=3 3>actual <<-EOF &&
+	commit refs/heads/N-empty-existing
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	read empty root directory via ls
+	COMMIT
+
+	ls ""
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'N: "ls" command can read subdir of named tree' '
+	branch_cmit=$(git rev-parse --verify refs/heads/branch^0) &&
+	subdir_tree=$(git rev-parse $branch_cmit:newdir) &&
+	echo "040000 tree $subdir_tree	newdir" >expect &&
+	git fast-import --cat-blob-fd=3 3>actual <<-EOF &&
+	commit refs/heads/N-subdir-of-named-tree
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	read from commit with ls
+	COMMIT
+
+	ls $branch_cmit "newdir"
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_failure 'N: "ls" command can read root of named commit' '
+	branch_cmit=$(git rev-parse --verify refs/heads/branch^0) &&
+	branch_tree=$(git rev-parse --verify $branch_cmit:) &&
+	echo "040000 tree $branch_tree	" >expect &&
+	git fast-import --cat-blob-fd=3 3>actual <<-EOF &&
+	commit refs/heads/N-root-of-named-tree
+	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+	data <<COMMIT
+	read root of commit with ls
+	COMMIT
+
+	ls $branch_cmit ""
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success PIPE 'N: read and copy root' '
-	cat >expect <<-\EOF
+	cat >expect <<-\EOF &&
 	:100755 100755 f1fb5da718392694d0076d677d6d0e364c79b0bc f1fb5da718392694d0076d677d6d0e364c79b0bc C100	file2/newf	file3/file2/newf
 	:100644 100644 7123f7f44e39be127c5eb701e5968176ee9d78b1 7123f7f44e39be127c5eb701e5968176ee9d78b1 C100	file2/oldf	file3/file2/oldf
 	:100755 100755 85df50785d62d3b05ab03d9cbf7e4a0b49449730 85df50785d62d3b05ab03d9cbf7e4a0b49449730 C100	file4	file3/file4